How can I use apt services on server side?

Hi,
I'm trying to use some apt service to work with plans on server side, but I got some strange error like the classes can't be found:

If I try to run command like these:

IPlanningCommon pc = (IPlanningCommon)getService(IPlanningCommon.class);

I obtain this kind of error:

ERROR t.internal.registry.AbstractActivationManagerOwner  - The class "com.ibm.team.apt.internal.common.IPlanningCommon" failed to load. The bundle "my.bundle.name" could not find the class.

The same for the com.ibm.team.apt.internal.common.rcp.IIterationPlanService class. But these classes/plugin are part of the SDK so I don't really understand why they are not found if used like other services as usual..

Any hints on how to use these class on server side?

Thanks,
Michele.